Poison bait for control of noxious insects

ABSTRACT

A bait composition in a tablet form, which comprises as the essential components (a) at least one insect-growth controlling agent selected from (a-1) insect juvenile hormone-like compounds and (a-2) insect chitin-synthesis inhibitors in a microencapsulated form and (b) dextrin, optionally with an additional or auxiliary agent(s).

The present invention pertains to a poison bait for control of noxious insects.

There have heretofore been commercially available some powdery posion baits for eradicating noxious insects such as cockroaches. These conventional poison baits in a powdery form are, however, practically disadvantageous and dangerous in causing many problems from the standpoints of sanitary and daily usages. For instance, they attach to the hands on handling, fly about the surroundings after being situated in desired places or are apt to be erroneously taken as food by infants and household pets.

In order to solve the above problems, poison baits in tablets were put into the market, which comprise boric acid as the active ingredient. For assurance of the eradicating effect, however, such poison bait tablets should contain boric acid in such a large amount as about 20 to about 30% by weight. Because of this, they are still not safe for infants and household pets. In fact, it is reported that even a baby powder containing boric acid in an amount of only 5% by weight accidentally produced the death of an infant (11th Japan Pharmacopoeia Commentary, C-1475 (1986)). In addition, bait containing boric acid makes cockroaches suffer from diarrhea and produce soft excrements, so that their habitats and surroundings are considerably stained thereby.

There are also known some poison baits in tablets, which comprise as the active ingredient an insecticide selected from organic phosphorus insecticides, carbamate insecticides, etc. However, those insecticides each have a characteristic odor, and a tablet preparation comprising any of them is apt to be repelled by cockroaches. Thus, the feeding attractant effect is much inferior, and naturally the eradicating effect is lowered. Further, said insecticides easily hydrolyze even with a slightest amount of water to produce a certain specific odor, thereby the feeding attractant effect is deteriorated and the eradicating effect is decreased. Said hydrolysis results in lowering of the content of the active ingredient itself, and the insecticidal effect is thus remarkably deteriorated.

A proposal was made to provide a poison bait composition in a tablet form which comprises at least one insect-growth controlling agent selected from insect juvenile hormone-like compounds and insect chitin-synthesis inhibitors in a microencapsulated form, and crystalline cellulose (JP-A-01-224307). However, incorporation of a feeding attractant of good efficacy such as animal powders and crushed biscuit into said composition tends to cause cracking of the resultant tablets, and tabletting is made impossible unless the feeding attractant is used in a finely pulverized state. Due to the above reason, the feeding attractant as usable is restricted to starches or sugars, and therefore the effect is not satisfactory.

There has thus been a great demand for a poison bait having a high safety to human beings as well as domestic animals, a remarkable feeding attractant effect and a sufficient insecticidal effect in addition to the safety on handling and the stability of the active ingredient.

As a result of extensive studies, it has now been found that a tabletted poison bait composition comprising a certain specific insect-growth controlling agent in a microencapsulated form in combination with some certain additives meets the above demand

According to the present invention, there is provided a tabletted poison bait composition, which comprises as the essential components (a) at least one insect-growth controlling agent selected from the group consisting of (a-1) insect juvenile hormone-like compounds and (a-2) insect chitin-synthesis inhibitors in a microencapsulated form and (b) dextrin, optionally with (c) at least one food attractant selected from the group consisting of (c-1) plant oils in an amount of not more than 10% by weight, (c-2) sugars in an amount of not more than 60% by weight, (c-3) cereal flours in an amount of not more than 50% by weight, (c-4) crushed biscuit in an amount of not more than 50% by weight and (c-5) animal powders in an amount of not more than 10% by weight of the total bait composition.

The bait composition comprising the above components can be stably formulated into a tablet and exerts a sufficient eradicating effect against harmful insects. The composition is also effective in inhibiting the emergence of insects as well as reducing reproductivity. Further, incorporation of sugars, cereal flours, crushed biscuit and/or animal powders as the additional components enhence the feeding attractant effect and the stability of the essential components.

As the component (a-1), there are exemplified dodecadienoate compounds, oxime ether compounds, pyridyl ether compounds, carbamate compounds, etc., of which representative compounds are shown in Table 1:

                  TABLE 1                                                          ______________________________________                                         Generic name                                                                   or code   Chemical name                                                        ______________________________________                                         Methoprene                                                                               Isopropyl (2E-4E)-11-methoxy-3,7,11-tri-                                       methyl-2,4-dodecadienoate                                            Hydroprene                                                                               Ethyl (2E-4E)-3,7,11-trimethyldodeca-2,4-                                      dienoate                                                             Pyriproxy-                                                                               2-[1-Methyl-2-(4-phenoxyphenoxy)ethoxy]-                             fen       pyridine                                                             S-21149   Propionaldehyde oxime O-2-(4-phenoxy-                                          pheoxy)ethyl ether                                                   S-21150   Propionaldehyde oxime O-2-(4-phenoxy-                                          pheoxy)propyl ether                                                  Fenoxycarb                                                                               O-Ethyl N-[2-(4-phenoxyphenoxy)ethyl]-                                         carbamate                                                            R-20458   1-(4-Ethylphenoxy)-6,7-epoxy-3,7-dimethyl-                                     2-octene                                                             ______________________________________                                    

As the component (a-2), benzoylphenyl urea compounds may be used, of which examples are shown in Table 2:

                  TABLE 2                                                          ______________________________________                                         Generic name                                                                   or code   Chemical name                                                        ______________________________________                                         Diflubenzu-                                                                              1-(4-Chlorophenyl)-3-(2,6-difluorobenzoyl)-                          ron       urea                                                                 Triflumu- 2-Chloro-N-[[[4-(trifluoromethoxy)phenyl]                            ron       amino]carbonyl]benzamide                                             EL 494    N-[[[5-(4-Bromophenyl)-6-methyl-2-pyradinyl]-                                  amino]carbonyl]-2,6-dichlorobenzamide                                Teflu-    1-(3,5-Dichloro-2,4-difluorophenyl)-3-(2,6-                          benzuron  difluorobenzoyl)urea                                                 Chlor-    1-[3,5-Dichloro-4-(3-chloro-5-trifluoro-                             fluazuron methyl-2-pyridyloxy)phenyl]-3-(2,6-di-                                         fluorobenzoyl)urea                                                   XRD-473   N-[[[3,5-Dichloro-4-(1,1,2,2-tetrafluoro-                                      ethoxy)phenyl]amino]carbonyl]-2,6-difluoro-                                    benzamide                                                            S-71624   N-2,6-Difluorobenzoyl-N'-[2-fluoro-4-(1,1,2,2-                                 tetrafluoroethoxy)phenyl]urea                                        S-71622   N-2,6-Difluorobenzoyl-N'-(2-fluoro-4-tri-                                      fluoromethylphenyl)urea                                              ______________________________________                                    

The components (a-1) and (a-2) as exemplified above may include their geometric isomers and optical isomers.

The amount of the insect-growth controlling agent (a) varies depending on the kind of the compound used and the target insect. Normally, however, the component (a) may be contained in an amount of about 0.01 to 2% by weight to the total composition.

For the use in this invention, insect-growth controlling agent is microencapsulated using any film-forming material. The film-forming material may be any one which can form a film having a strength tolerable to the impact which will be applied thereto at the subsequent tabletting step, and examples thereof are polyureas, polyurethanes, polyamides, polyesters, polycarbonates, polysulfonates, polysulfonamides, epoxy resins, etc. Microencapsulation may be carried out by a per se conventional procedure, of which typical examples are interfacial polymerization process, in-situ polymerization process, drying in liquid process, phase separation process, spray drying process, fluidized bed process, cooling melted dispersion process, etc. Among them, interfacial polymerization process is preferred, because the particle size can be easily controlled. It is desirable that the microcapsules have an average particle size of about 1 to about 1,000 microns and a particle size/film thickness ratio of about 10 to about 140. Tabletting is normally effected under a compression of about 10 to about 500 kg/cm².

Dextrin as the component (b) may be a product of starch powders (e.g. potato, sweet potato, corn, wheat, rice) hydrolyzed with an acid, heat or amylase. It is normally used in an amount of about 10 to about 99% by weight to the total weight of the bait composition.

In addition to the above essential components, the bait composition may comprise optionally at least one feeding attractant (c) chosen from (c-1) plant oils, (c-2) sugars, (c-3) cereal flours, (c-4) crushed biscuit and (c-5) animal powders. Specific examples of the plant oils are soybean oil, rapeseed oil, sesame oil, wheat germ oil, etc. The amount to be used may be 0 to about 50% by weight to the total composition. As the sugars, there may be exemplified sucrose, glucose, fructose, lactose, black sugar, brown sugar, soft brown sugar, etc., among which black sugar, brown sugar and soft brown sugar are particularly preferred. The sugars are normally used in an amount of 0 to about 60% by weight of the total composition. The cereal flours may be, for instance, potato powders, sweet potato powders, corn powders, wheat flours, rice powders, corn flours, etc., the amount of which may be, for instance, 0 to about 50% by weight. The crushed biscuit may be any of the commercial products on the market and is used in an amount of 0 to about 50% by weight. Examples of the animal powders are fish powders, chrysalis powders, Euphauciasea powders, shrimp powders, etc. These may be used in an amount of 0 to about 10% by weight of the total composition.

When desired, the bait composition may further comprise an additive(s) and/or an auxiliary agent(s), particularly an anti-oxidizing agent, a preservative, a mis-feeding inhibitor, a flavoring agent, a filler, etc. Examples of the anti-oxidizing agent are erythorbic acid, sodium erythorbate, dibutyl hydroxytoluene, dl-alphatocoptelol, nordihydroguaiaretic acid, methylhydroxyanisole, propyl gallate, guaiac resin, L-cysteine hydrochloride, etc. Examples of the preservative are benzoic acid, sodium benzoate, salicylic acid, diphenyl, sorbic acid, potassium sorbate, dehydroacetic acid, sodium dehydroacetate, isobutyl p-oxybenzoate, isopropyl p-oxybenzoate, ethyl p-oxybenzoate, butyl p-oxybenzoate, propyl p-oxybenzoate, calcium propionate, sodium propionate, etc. As the mis-feeding inhibitor, there may be exemplified red pepper powders, Amaranth, Amaranth aluminium lake, Erythrosine, Erythrosine aluminium lake, New Coccine, Phloxine, Rose Bengal, Acid Red, Tartrazine, Tartrazine aluminium lake, Sunset Yellow FCF, Sunset Yellow FCF aluminium lake, Fast Green FCF, Fast Green FCF aluminium lake, Brilliant Blue FCF, Brilliant Blue FCF aluminium lake, Indigo Carmine, Indigo Carmine aluminium lake, beta-carotene, copper chlorophyll, etc. Examples of the flavoring agent are cheese flavor, butter flavor, peanut flavor, peach flavor, strawberry flavor, milk flavor, etc. As the filler, there may be used calcium silicate, diatomaceous earth, crystalline celllulose, clay, kaolin, talc, bentonite, zeolite, sepiolite, attapulgite, etc.

For preparation of the poison bait composition of the invention, the essential and optional components as above mentioned may be mixed together to make a uniform mixture, which is then subjected to tabletting by a per se conventional procedure. For instance, one or more insect-growth contolling agents as microencapsulated are mixed with dextrin and a food attractant to make a uniform mixture, which is then tabletted by a per se conventional procedure to produce a bait composition in a tablet form of desired size. When two or more insect-growth controlling agents are used, each of them or a mixture of them may be microencapsulated; if necessary, two or more agents may be each microencapsulated and combined together, followed by microencapsulation of the resultant mixture.

The thus obtained bait composition exerts a remarkable insecticidal effect against a wide range of harmful insects, of which examples are cockroaches (Blattidae) such as American cockroach (Periplaneta americana), German cockroach (Blattella germanica) and smokybrown cockroach (Periplaneta fuliginosa, ants (Formicidae) such as Monomorium sp. and Formica japonica, deathwatch and drugstore beetles (Anobiidae) such as cigarette beete (Lasioderma serricorne) and biscuit beetle (Stegobium paniceum), darkling beetles (Tenebrionidae) such as red flour beetle (Tribolium castaneum) and confused flour beetle (Tribolium confusum) and cucujid beetles (Cucujidae) such as saw-toothed grain beetle (Oryzaephilus surinamensis) and flat grain beetle (Cryprolestes pusillus), termites (Isoptera) such as Formosan subterranean termite (Coptotermes formosanus) and Reticulitermes speratus, etc.

Practical embodiments for preparation of the insecticidal composition according to the invention are illustratively shown in the following examples wherein % are by weight unless otherwise indicated.

EXAMPLES 1 TO 6

Pyriproxyfen (0.05%) microencapsulated with polyurethane, dextrin (99.85% in Example 1; 30.0% in Examples 2 to 6) and dehydroacetic acid (0.1%) were mixed together, and an essential oil, sugar, cereal flours, crushed biscuit and animal powders as shown in Table 3 were incorporated therein, followed by mixing uniformly. The resultant mixture was tabletting under a compression of 15 kg/cm² to make tablets, each weighing about 4 g (diameter, about 30 mm).

The thus obtained tablets as a bait were subjected to evaluation of the tablettability, the stability of the active ingredient, the feeding attractant effect, the inhibitory effect on emergence and the inhibitory effect on reproduction according to the following procedures, and the results are shown in Table 3:

1) Tabletability:

Observation was made immediately after tabletting and also after 10 days storage at 50° C., and the tabletability was evaluated with respect to production of cracks: (O) no crack; (X) cracks.

2) Stability of the active ingredient:

The bait in a tablet form was kept at 50° C. for 10 days and subjected to measurement of the residual percent of the active ingredient by gas chromatography. Evaluation was based on the following criteria:

    ______________________________________                                         Criteria     Residual percent                                                  ______________________________________                                         ++           >80%                                                              +            70-80%                                                            -            <70%                                                              ______________________________________                                    

3) Feeding attractant effect (i.e., effect in attracting and stimulating the insects to eat food):

Fifty imagos of Blattella germanica (even numbers of male and female) were admitted in a container having a bottom area of 0.12 m² where the bait in a tablet form as well as a solid bait as control were placed. The attractant rate was calculated on the basis of the numbers of insects attracted by the bait within a designated period and classified on the following criteria:

    ______________________________________                                         Criteria     Attractant rate                                                   ______________________________________                                         ++           >80%                                                              +            70-80%                                                            -            <70%                                                              ______________________________________                                    

4) Inhibitory effect on emergence:

Ten last instar larvae of Blattella germanica (even numbers of male and female) were admitted in a container having a bottom area of 100 cm² where the bait in a tablet form as well as a solid bait as control were placed, and observation was made on failure of emergence, abnormality of wings and supernumerary molting over a period of three weeks. The number of failures in emergence, abnormality normality of wings and supernumerary molting was determined to calculate the emergence inhibitory rate, and the results are classified on the following criteria:

    ______________________________________                                         Criteria   Emergence inhibitory rate                                           ______________________________________                                         ++         >80%                                                                +          70-80%                                                              -          <70%                                                                ______________________________________                                    

5) Inhibitory effect on reproduction:

Ten last instar larvae of Blattella germanica (even numbers of male and female) were admitted in a container having a bottom area of 100 cm² where the bait in a tablet form as well as a solid bait as comparison were placed, and the number of hatched eggs and the rate of emergence were observed over a period of four weeks. Reduction in the number of the next generation in contrast to the untreated group was calculated, and the results were classified on the following criteria:

    ______________________________________                                                      Reduction in the                                                  Criteria     next generation                                                   ______________________________________                                         ++           >80%                                                              +            70-80%                                                            -            <70%                                                              ______________________________________                                    

                                      TABLE 3                                      __________________________________________________________________________                        Example                                                                        1  2  3  4  5  6                                            __________________________________________________________________________     Composi-                                                                             Pyriproxyfen*.sup.1)                                                                         0.05                                                                              0.05                                                                              0.05                                                                              0.05                                                                              0.05                                                                              0.05                                        tion  Dextrin      99.85                                                                             30.0                                                                              30.0                                                                              30.0                                                                              30.0                                                                              30.0                                         (%)   Dehydroacetic                                                                               0.1                                                                               0.1                                                                                0.1                                                                               0.1                                                                               0.1                                                                              0.1                                                acid                                                                     Plant        Sesame                                                                               -- 2.0                                                                               --  2.0                                                                              -- 2.0                                          oil          oil                                                                            Corn  -- -- 10.0                                                                              -- -- --                                                        oil                                                               Sugar        Black -- -- 20.0                                                                              -- -- 10.0                                                      sugar                                                                          Brown -- -- -- 50.0                                                                              -- --                                                        sugar                                                                          Soft  -- -- -- -- 10.0                                                                              --                                                        brown                                                                          sugar                                                             Starch       Potato                                                                               -- 50.0                                                                              33.0                                                                              10.0                                                                               9.4                                                                              --                                           powder       starch                                                            Crushed biscuit    -- -- -- -- 50.0                                                                              40.0                                         Animal       Euphau-                                                                              -- 2.5                                                                               -- -- -- 5.0                                          powder       siacea                                                                         powder                                                                         Chry- -- 2.5                                                                               -- -- -- 5.0                                                       salis                                                                          powder                                                            Calcium silicate   -- 12.85                                                                              9.85                                                                              7.85                                                                             --  4.85                                        Evalu-                                                                               Tablet-                                                                               A*.sup.2)                                                                            ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                ation ability                                                                               B*.sup.3)                                                                            ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                Stability of active                                                                               ++ ++ ++ ++ ++ ++                                           ingredient                                                                     Feeding      A     ++ ++ ++ ++ ++ ++                                           attractant   B     ++ ++ ++ ++ ++ ++                                           effect                                                                         Emergence    A     ++ ++ ++ ++ ++ ++                                           inhibitory   B     ++ ++ ++ ++ ++ ++                                           effect                                                                         Reproduc-    A     ++ ++ ++ ++ ++ ++                                           tion         B     ++ ++ ++ ++ ++ ++                                           control                                                                        effect                                                                         __________________________________________________________________________      Note:                                                                          *.sup.1) microencapsulated with polyurethane.                                  *.sup.2) immediately after tableting.                                          *.sup.3) after being kept at 50° C. for 10 days.                  

EXAMPLES 7 TO 9

In the same manner as in Examples 1 to 6, there were prepared tablets as a bait comprising the components as shown in Table 4. The thus obtained tablets were subjected to evaluation of various properties in the same manner as in Examples 1 to 6, the results of which are also shown in Table 4.

COMPARATIVE EXAMPLES 1 TO 3

In the same manner as in Examples 7 to 9 but using an insect-growth controlling agent that was not microencapsulated, there were prepared tablets as a bait, and evaluation of these baits was made in the same manner as in Examples 7 to 9. The results are also shown in Table 4.

                                      TABLE 4                                      __________________________________________________________________________                        Example  Comparative                                                           7  8  9  1  2  3                                            __________________________________________________________________________     Composi-                                                                             Hydroprene*.sup.1)                                                                          0.5                                                                               -- -- -- -- --                                           tion               -- -- -- 0.5                                                                               -- --                                           (%)   Teflubenzuron*.sup.2)                                                                       -- 0.7                                                                               -- -- -- --                                                              -- -- -- -- 0.7                                                                               --                                                 Diflubenzuron*.sup.2)                                                                       -- -- 1.0                                                                               -- -- --                                                              -- -- -- -- -- 1.0                                                Dextrin      50.0                                                                              50.0                                                                              50.0                                                                              50.0                                                                              50.0                                                                              50.0                                               Cheese flavoring                                                                            0.3                                                                               0.3                                                                               0.3                                                                               0.3                                                                               0.3                                                                               0.3                                                agent                                                                          Black sugar  10.0                                                                              10.0                                                                              10.0                                                                              10.0                                                                              10.0                                                                              10.0                                               Crushed biscuit                                                                             34.2                                                                              34.0                                                                              33.7                                                                              34.2                                                                              34.0                                                                              33.7                                         Animal       Euphau-                                                                              2.5                                                                               2.5                                                                               2.5                                                                               2.5                                                                               2.5                                                                               2.5                                          powder       siacea                                                                         powder                                                                         Chry- 2.5                                                                               2.5                                                                               2.5                                                                               2.5                                                                               2.5                                                                               2.5                                                       salis                                                                          powder                                                            Evalu-                                                                               Tablet-                                                                               A*.sup. 3)                                                                           ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                ation ability                                                                               B*.sup.4)                                                                            ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                Stability of active                                                                               ++ ++ ++ +  +  +                                            ingredient                                                                     Feeding      A     ++ ++ ++ ++ ++ ++                                           attractant   B     ++ ++ ++ +  +  +                                            effect                                                                         Emergence    A     ++ ++ ++ ++ ++ ++                                           inhibitory   B     ++ ++ ++ -  -  -                                            effect                                                                         Reproduc-    A     ++ ++ ++ ++ ++ ++                                           tion         B     ++ ++ ++ -  -  -                                            control                                                                        effect                                                                         __________________________________________________________________________      Note:                                                                          *.sup.1) microencapsulated with polyurethane.                                  *.sup.2) microencapsulated with polyurea.                                       *.sup.3) immediately after tableting.                                         *.sup.4) after being kept at 50° C. for 10 days.                  

EXAMPLES 10 TO 16

In the same manner as in Examples 1 to 9, there were prepared tablets comprising the components as shown in Table 5. Various properties of the tablets were evaluated, and the results are shown in Table 5, from which it is understood that the tablets exhibit an excellent properties and no cracks or damage are produced on tabletting.

                                      TABLE 5                                      __________________________________________________________________________                        Example                                                                        10 11 12 13 14 15 16                                        __________________________________________________________________________     Composi-                                                                            Hydroprene*.sup.1)                                                                           0.5                                                                               -- -- -- -- -- --                                        tion S-21149*.sup.2)                                                                              --  0.05                                                                             -- -- -- -- --                                        (%)  Fenoxycarb*.sup.1)                                                                           -- -- 0.1                                                                               -- -- -- --                                             Triflumuron*.sup.1)                                                                          -- -- -- 0.5                                                                               -- -- --                                             Chlorfluazuron*.sup.1)                                                                       -- -- -- -- 0.5                                                                               -- --                                             S-71624*.sup.1)                                                                              -- -- -- -- -- 0.5                                                                               --                                             S-71622*.sup.1)                                                                              -- -- -- -- -- --  0.05                                          Dextrin       72.4                                                                              59.85                                                                             37.0                                                                              97.5                                                                              52.4                                                                              67.4                                                                              67.85                                          Potato starch -- -- -- -- -- -- --                                        Plant oil   Sesame oil                                                                            2.0                                                                               -- -- -- 2.0                                                                               2.0                                                                               2.0                                                   Corn oil                                                                              -- -- 2.0                                                                               2.0                                                                               -- -- --                                        Sugar       Black sugar                                                                           20.0                                                                              -- -- -- 20.0                                                                              10.0                                                                              10.0                                                  Brown sugar                                                                           -- 20.0                                                                              -- -- -- -- --                                                    Soft brown                                                                            -- -- 20.0                                                                              -- -- -- --                                                    sugar                                                              Crushed biscuit    -- 20.0                                                                              20.0                                                                              -- 20.0                                                                              10.0                                                                              10.0                                      Animal      Euphausi-                                                                             2.5                                                                               -- 5.0                                                                               -- 2.5                                                                               10.0                                                                              10.0                                      powder      acea powder                                                                    Chrysalis                                                                             2.5                                                                               -- 5.0                                                                               -- 2.5                                                                               -- --                                                    powder                                                             Red pepper powder  -- -- 0.5                                                                               -- -- -- --                                        Red pigment No. 1  -- -- -- -- trace                                                                             trace                                                                             trace                                     Butter flavoring   -- -- 0.3                                                                               -- -- -- --                                        agent                                                                          Calcium silicate   -- -- 10.0                                                                              -- -- -- --                                        Dehydroacetic acid 0.1                                                                               0.1                                                                               0.1                                                                               -- 0.1                                                                               0.1                                                                               0.1                                       Evalu-                                                                              Tabletability                                                                         A*.sup.3)                                                                             ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                             ation       B*.sup.4)                                                                             ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                             Stability of active                                                                               ++ ++ ++ ++ ++ ++ ++                                        ingredient                                                                     Feeding at- A      ++ ++ ++ ++ ++ ++ ++                                        tractant    B      ++ ++ ++ ++ ++ ++ ++                                        effect                                                                         Emergence   A      ++ ++ ++ ++ ++ ++ ++                                        inhibitory  B      ++ ++ ++ ++ ++ ++ ++                                        effect                                                                         Reproduction                                                                               A      ++ ++ ++ ++ ++ ++ ++                                        control     B      ++ ++ ++ ++ ++ ++ ++                                        effect                                                                         __________________________________________________________________________      Note:                                                                          *.sup.1) microencapsulated by polyurethane.                                    *.sup.2) microencapsulated by polyurea.                                        *.sup.3) immediately after tableting.                                          *.sup.4) after being kept at 50° C. for 10 days.                  

COMPARATIVE EXAMPLES 4 TO 10

In the same manner as in Examples 10 to 16 but using potato starch instead of dextrin, there were prepared tablets as shown in Table 7. Various properties of these tablets were observed in the same manner as in Examples 10 to 16, and the results are shown in Table 7. It was noticeable that the tablets thus formulated had many cracks or damage. The feeding attractant effect, emergence inhibitory effect and reproduction control effect were deteriorated.

                                      TABLE 7                                      __________________________________________________________________________                        Comparative Example                                                            4  5  6  7  8  9  10                                        __________________________________________________________________________     Composi-                                                                            Hydroprene*.sup.1)                                                                           0.5                                                                               -- -- -- -- -- --                                        tion S-21149*.sup.2)                                                                              --  0.05                                                                             -- -- -- -- --                                        (%)  Fenoxycarb*.sup.1)                                                                           -- -- 0.1                                                                               -- -- -- --                                             Triflumuron*.sup.1)                                                                          -- -- -- 0.5                                                                               -- -- --                                             Chlorfluazuron*.sup.1)                                                                       -- -- -- -- 0.5                                                                               -- --                                             S-71624*.sup.1)                                                                              -- -- -- -- -- 0.5                                                                               --                                             S-71622*.sup.1)                                                                              -- -- -- -- -- --  0.05                                          dextrin       -- -- -- -- -- -- --                                             Potato starch 72.4                                                                              59.85                                                                             37.0                                                                              97.5                                                                              52.4                                                                              67.4                                                                              67.85                                     Plant oil   Sesame oil                                                                            2.0                                                                               -- -- -- 2.0                                                                               2.0                                                                               2.0                                                   Corn oil                                                                              -- -- 2.0                                                                               2.0                                                                               -- -- --                                        Sugar       Black sugar                                                                           20.0                                                                              -- -- -- 20.0                                                                              10.0                                                                              10.0                                                  Brown sugar                                                                           -- 20.0                                                                              -- -- -- -- --                                                    Soft brown                                                                            -- -- 20.0                                                                              -- -- -- --                                                    sugar                                                              Crushed biscuit    -- 20.0                                                                              20.0                                                                              -- 20.0                                                                              10.0                                                                              10.0                                      Animal      Euphausi-                                                                             2.5                                                                               -- 5.0                                                                               -- 2.5                                                                               10.0                                                                              10.0                                      powder      acea powder                                                                    Chrysalis                                                                             2.5                                                                               -- 5.0                                                                               -- 2.5                                                                               -- --                                                    power                                                              Red pepper powder  -- -- 0.5                                                                               -- -- -- --                                        Red pigment No. 1  -- -- -- -- trace                                                                             trace                                                                             trace                                     Butter flavoring   -- -- 0.3                                                                               -- -- -- --                                        agent                                                                          Calcium silicate   -- -- 10.0                                                                              -- -- -- --                                        Dehydroacetic acid 0.1                                                                               0.1                                                                               0.1                                                                               -- 0.1                                                                               0.1                                                                               0.1                                       Evalu-                                                                              Tabletability                                                                         A*.sup.3)                                                                             X  X  X  X  X  X  X                                         ation       B*.sup.4)                                                                             X  X  X  X  X  X  X                                         Stability of active                                                                               ++ ++ ++ ++ ++ ++ ++                                        ingredient                                                                     Feeding at- A      +  +  +  +  +  +  +                                         tractant    B      +  +  +  +  +  +  +                                         effect                                                                         Emergence   A      +  +  +  +  +  +  +                                         inhibitory  B      +  +  +  +  +  +  +                                         effect                                                                         Reproduction                                                                               A      +  +  +  +  +  +  +                                         control     B      +  +  +  +  +  +  +                                         effect                                                                         __________________________________________________________________________      Note:                                                                          *.sup.1) microencapsulated by polyurethane.                                    *.sup.2) microencapsulated by polyurea.                                        *.sup.3) immediately after tableting.                                          *.sup.4) after being kept at 50° C. for 10 days.                  

As shown by the foregoing results, the tablets according to the present invention are quite satisfactory in stability, feeding attractant effect, emergence inhibitory effect and reproduction control effect. Further, since no cracks or damage occur during tabletting, the composition of the invention is useful as a bait for harmful insects such as cockroaches. 

What is claimed is:
 1. A poisonous tablet bait composition, which comprises as the essential components (a) at least one insect-growth controlling agent selected from the group consisting of an (a-1) insect juvenile hormone-like compound and (a-2) an insect chitin-synthesis inhibitor in a microencapsulated form in an amount of 0.01 to 2% by weight, and (b) dextrin in an amount of 10 to 99% by weight of the total composition.
 2. The composition according to claim 1, which further comprises (c) at least one feeding attractant selected from the group consisting of (c-1) plant oils in an amount of not more than 10% by weight, (c-2) sugars in an amount of not more than 60% by weight, (c-3) cereal flours in an amount of not more than 50% by weight, (c-4) crushed biscuit in an amount of not more than 50% by weight and (c-5) animal powders in an amount of not more than 10% by weight of the total composition.
 3. A method for controlling noxious insects, which comprises applying said bait composition according to claim 1 to the area where said insects inhabit.
 4. The method according to claim 3, wherein said noxious insects belongs to the families Blattidae, Formicidae, Anobiidae, Tenebrionidae, Cucujidae or Isoptera.
 5. A process for preparing a tablet poison bait composition, which comprises uniformly mixing as the essential components (a) at least one insect-growth, controlling agent selected from the group consisting of (a-1) insect juvenile hormone-like compounds and (a-2) insect chitin-synthesis inhibitors in a microencapsulated form, and (b) dextrin, optionally with any additional component(s), and tabletting the mixture in a tablet form of desired size.
 6. The composition according to claim 1, wherein said insect-growth controlling agent is at least one member selected from the group consisting of isopropyl (2E-4E)-11-methoxy-3,7,11-trimethyl-2,4-dodecadienoate; ethyl (2E-4E)-3,7,11-trimethyldodeca-2,4-dienoate; 2-[1-methyl-2-(4-phenoxy-phenoxy)ethoxy]pyridine; propionaldehyde oxime O-2-(4-phenoxypheoxy)ethyl ether; propionaldehyde oxime O-2-(4-phenoxypheoxy) propyl ether; O-ethyl N-[2-(4-phenoxyphenoxy)ethyl]carbamate; 1-(4-ethylphenoxy)- 6,7-epoxy-3,7-dimethyl-2-ocete; 1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea; 2-chloro-N-[[[4-trifluoromethoxy)phenyl]amino]carbonyl]benzamide; N-[[[5-(4-bromophenyl)-6-methyl-2-pyradinyl]amino]carbonyl]-2,6-dichlorobenzamide; 1-(3,5-dichloro-2,4-difluorophenyl)-3-(2,6-difluorobenzoyl)urea; 1-[3,5-dichloro-4-(3-chloro-5-trifluoro-methyl-2-pyridyloxy)phenyl]-3-(2,6-difluorobenzoyl)urea; N-[[[3,5-dichloro-4-(1,1,2,2-tetrafluoroethoxy)phenyl]amino]carbonyl]-2,6-difluorobenzamide; N-2,6-difluorobenzoyl-N'-[2-fluoro-4-(1,1,2,2-tetrafluoroethoxy)phenyl]urea; N-2,6-difluorobenzoyl-N'-(2-fluoro-4-trifluoromethylphenyl)urea, a geometric isomer thereof; and an optical isomer thereof.
 7. The composition according to claim 2, wherein said plant oils are selected from the group consisting of soybean oil, rapeseed oil, sesame oil and wheat germ oil in an amount of 0 to about 50% by weight, said sugars are selected from the group consisting of sucrose, glucose, fructose, lactose, black sugar, brown sugar and soft brown sugar, said cereal flours are selected from the group consisting of potato powders, sweet potato powders, corn powders, wheat powders, rice powders and corn flours in an amount of 0 to about 50% by weight, and said animal powders are selected from the group consisting of fish powders, chrysalis powders, Euphauciasea powders and shrimp powders in an amount of 0 to about 10% by weight of the total composition.
 8. The composition according to claim 1, wherein said insect juvenile hormone-like compound (a-1) is selected from the group consisting of a dodecadienoate compound, an oxime ether compound, a pyridyl ether compound, and a carbamate compound, and said insect chitin-synthesis inhibitor is a benzoylphenyl urea compound.
 9. The composition according to claim 1, wherein said insect-growth controlling agent is microencapsulated in a film-forming material selected from the group consisting of a polyurea, a polyurethane a polyamide, a polyester, a polycarbonate, a polysulfonate, a polysulfonamide, and an epoxy resin.
 10. The composition according to claim 1, wherein dextrin component (b) is a hydrolyzed starch powder product.
 11. The composition according to claim 10, wherein said starch powder is selected from the group consisting of potato powder, sweet potato powder, corn powder, wheat powder, and rice powder.
 12. The composition according to claim 7, wherein said sugars are selected from the group consisting of black sugar, brown sugar, and soft brown sugar.
 13. The composition according to claim 1, which further comprises at least one additive and/or auxiliary agent.
 14. The composition according to claim 13, wherein said additive or auxiliary agent is selected from the group consisting of an anti-oxidizing agent, a preservative, a mis-feeding inhibitor, a flavoring agent, and a filler.
 15. The composition according to claim 14, wherein said anti-oxidizing agent is selected from the group consisting of erythorbic acid, sodium erythorbate, dibutyl hydroxytoluene, dl-alphatocophelol, nordihydroguaiaretic acid, methylhydroxyanisole, propyl gallate, guaiac resin, and L-cysteine hydrochloride, said preservative is selected from the group consisting of benzoic acid, sodium benzoate, salicylic acid, diphenyl, sorbic acid, potassium sorbate, dehydroacetic acid, sodium dehydroacetate, isobutyl p-oxybenzoate, isopropyl p-oxybenzoate, ethyl p-oxybenzoate, butyl p-oxybenzoate, propyl p-oxybenzoate, calcium propionate, and sodium propionate, said mis-feeding inhibitor is selected from the group consisting of red pepper powders, Amaranth, Amaranth aluminium lake, Erythrosine, Erythrosine aluminium lake, New Coccine, Phloxine, Rose Bengal, Acid Red, Tartrazine, Tartrazine aluminium lake, Sunset Yellow FCF, Sunset Yellow FCF aluminium lake, Fast Green FCF, Fast Green FCF aluminium lake, Brilliant Blue FCF, Brilliant Blue FCF aluminium lake, Indigo Carmine, Indigo Carmine aluminium lake, beta-carotene, and copper chlorophyll, said flavoring agent is selected from the group consisting of cheese flavor, butter flavor, peanut flavor, peach flavor, strawberry flavor, and milk flavor, and said filler is selected from the group consisting of calcium silicate, diatomacaeous earth, crystalline cellulose, clay, kaoline, talc, bentonite, zeolite sepiolite, and attapulgite. 